The present invention relates to a semiconductor manufacturing apparatus and, more particularly, to a diffusion furnace or a vapor phase growth furnace.
FIGS. 2A to 2D illustrate a sequence of operations of a conventional diffusion furnace or vapor phase growth furnace. This furnace comprises a cap-like core tube 1, a heater 2 arranged around the outer surface of the core tube 1, a shutter 3 which is formed at the lower end opening of the core tube 1 and is opened/closed when semiconductor substrates 6 are loaded/unloaded, a gas introduction portion 4 which is connected to the upper central portion of the core tube 1, and an exhaust portion 5 which is connected to the lower inner side wall of the core tube 1 and designed to exhaust gas after reaction (FIG. 2A). When the semiconductor substrates 6 are to be subjected to annealing or a thin-film formation process, the shutter 3 is opened, and a boat 7 having the semiconductor substrates 6 mounted thereon is loaded into the core tube 1 (FIG. 2B). If necessary, a reaction gas is then introduced through the gas introduction portion 4 annealing the substrates 6 (FIG. 2C). Thereafter, the shutter 3 is opened (FIG. 2D) to unload the semiconductor substrates 6 from the core tube 1.
In the conventional diffusion furnace or vapor phase growth furnace, since the semiconductor substrates 6 are loaded and unloaded through the same opening by means of the shutter 3, semiconductor wafers located at upper and lower portions X and Y on the boat 7 in the core tube 1 have different thermal hysteresis. In addition, since atmospheric air flows into the furnace when the shutter 3 is opened, uniformity in film thickness among the respective semiconductor substrates is degraded.